SQL-Server: Truncate of transaction-logs inf FULL-BACKUP-Mode - sql-server

I found a link expaining very well the main factors of transaction-log. But there is 1 statements I don't understand completly:
The FULL recovery model means that every part of every operation is
logged, which is called being fully logged. Once a full database
backup has been taken in the FULL recovery model, the transaction log
will not automatically truncate until a log backup is taken. If you do
not want to make use of log backups and the ability to recover a
database to a specific point in time, do not use the FULL recovery
model. However, if you wish to use database mirroring, then you have
no choice, as it only supports the FULL recovery model.
My question are:
Will the transaction-logs get truncated if I have a database in Full-Backup-Mode but have neither taken an full-backup than an log-backup? Will the free space overwriten after next checkpoint? And when will those checkpoints be reached? Do I need to set a soze limit for the transaction logs to force the truncation or not?
Many thanks in advance

When your database is in full recovery mode,only log backup frees the space in log file..
This space won't be available for file system,but will be internally marked as free,so that new transactions can use this space
Will the free space overwriten after next checkpoint? And when will those checkpoints be reached? Do I need to set a size limit for the transaction logs to force the truncation or not?
You need not do anything,just ensure log backups are taken depending on your requirements

Related

SQL Server Log File Size

Apologies if this question was asked by someone.
I'm not much experienced in SQL server.
On our SQL server, there is 1 TB plus log file size.
Database is in full recovery.
Had taken an initial full backup and set a regular backup job for a transaction log for a stop to growing log file size too much.
so my question is, can I truncate my log file after taking log backup.
If there was abnormal event like long running transaction or huge data import, you restore the previous size with the code below:
DBCC SHRINKFILE(2,TRUNCATEONLY);
ALTER DATABASE [StackOverflow] MODIFY FILE (NAME = N'StackOverflow_Log', SIZE = 256MB);
The SHRINKFILE second argument is the file_id:
SELECT *
FROM sys.database_files;
Also, sometimes having a huge log file might be something normal. It basically depends on the activity on your database. So, 256 MB might be more or less. It will be better to set a size, which will be enough for handling your normal workload without growing.
You should also check how often you are performing backup of the log file - each 10 minute or each 1 hour.

Sql Server LDF file taking too large space

Why is my database log file taking to high space? Its almost taking up 30GB of my HDD. Even after deleting 1,000,000 records, its not freeing up any space.
So,
1.Why is the log file taking this much space (30gb)?2.how can I free up the space?
1.Why is the log file taking this much space (30gb)?
Or because of your recovery not SIMPLE and ldf grown eventually to such size
Or because there was a large one-time DML operation
Or because of other reasons, as noted by #sepupic in another answer
2.how can I free up the space?
IF recovery is other than SIMPLE:
Firstly backup transaction log file
Perform a shrink, like DBCC SHRINKFILE(2,256)
IF recovery is SIMPLE:
Just shrink it to desired size, like DBCC SHRINKFILE(2,256)
If the database log still did not reduce to a target size, then the exact reason to be checked, by using a code snippet of #sepupic
Some members still give and advice to physicaly remove LDF files.
I highly suggest to not do this. Remarkable related post of Aaron Bertrand:
Some things you don't want to do:
Detach the database, delete the log file, and re-attach. I can't
emphasize how dangerous this can be. Your database may not come back
up, it may come up as suspect, you may have to revert to a backup (if
you have one), etc. etc.
1. Why is the log file taking this much space (30gb)?
It was because the Autogrowth / Maxsize was set 200,000 MB
2. how can I free up the space?
As described Here i used the following command and the file is now less than 200mb
ALTER DATABASE myDatabaseName
SET RECOVERY SIMPLE
GO
DBCC SHRINKFILE (myDatabaseName_log, 1)
GO
ALTER DATABASE myDatabaseName_log
SET RECOVERY FULL
I have also set Autogrowh/Maxsize in the database properties to 1000 as Limited (See the image below).
The link describes more, so I recommend referring it for detailed description and other options.
Thanks #hadi for the link.
Why is my database log file taking to high space?
There can be more causes, not only the 2 mentioned in another answer.
You can find the exact reason using this query:
select log_reuse_wait_desc
from sys.databases
where name = 'myDB';
Here is a link to the BOL article that describes all the possible causes under log_reuse_wait:
sys.databases (Transact-SQL)
how can I free up the space?
First you should determine the cause using the query above, then you should fix it, for example, if it's broken replication you should remove it or fix it.
You need a maintenance job to backup the transaction log, and do it often: like every 10 minutes or so.
A FULL backup once per day isn't good enough.
Alternatively, you can change the Recovery Model of the database from FULL to SIMPLE. But if you do this, you'll lose the ability to do point-in-time restores.
In my case the DB names was with bad characters so the script doesn't worked.
I found out and follow this article, which worked perfect in two steps: changing backup log from full to simple and shrink DB log file more than 95%

Why does my SQL Server logfile have 99% space available after giving me a full warning?

While deleting a large number of records, I get this error:
The transaction log for database 'databasename' is full
I found this answer very helpful, it recommends:
Right-click your database in SQL Server Manager, and check the Options page.
Switch Recovery Model from Full to Simple
Right-click the database again. Select Tasks Shrink, Files Shrink the log file to a proper size (I generally stick to 20-25% of the size of the data files)
Switch back to Full Recovery Model
Take a full database backup straight away
Question: in step 3, when I go to shrink > files and choose log from the file type dropdown menu, it tells me that 99% of the allocated space is free.
Out of ~4500MB of allocated space, there is ~4400MB free (the data file size is ~3000MB).
Does that mean I'm good to go, and there is no need to shrink?
I don't understand this. Why would that be the case, given the warning I received initially?
I'm not one for hyperbole, but there are literally billions of articles written about SQL Server transaction logs.
Reader's digest version: if you delete 1,000,000 rows at a time, the logs are going to get large because it is writing those 1,000,000 deletes in case it has to roll back the transaction. The space needed to hold those records does not get released until the transaction commits. If your logs are not big enough to hold 1,000,000 deletes, the log will get filled, throw that error you saw, and rollback the whole transaction. Then all that space will most likely get released. Now you have a big log with lots of free space.
You probably hit a limit on your log file at 4.5gb and it wont get any bigger. To avoid filling your logs in the future, chunk down your transactions to smaller amounts, like deleting 1,000 records at a time. A shrink operation will reduce the physical size of the file, like from 4.5gb down to 1gb.
https://learn.microsoft.com/en-us/sql/t-sql/database-console-commands/dbcc-shrinkfile-transact-sql?view=sql-server-2017

Disk space constraint when attempting to delete data from DB

I need to delete some old logs from the database, however due to lack of space in the physical hard disk, there isn't enough space to sustain the growth of transaction log resulting from the delete activity.
My question is:
If i were to write a cursor to delete the data, would this action still contribute to the transaction log growth from this activity? I think yes, but just to confirm.
If #1 is not an option, then what else can I try? Physical disk space increase is not an option either.
Hope I've provided sufficient information to get some help. Please let me know if more is required.
Thanks in advance for any help received.
#GarethD is this a viable solution?
Perform full backup of the entire database into a remote location – ensure that this backup copy can be restored successfully.
Assuming that you wish to retain the data from years 2012 to present day, export out ONLY all the data that you wish to retain from UGCALL.
Ensure that this export can be imported into an empty table successfully and the data is not corrupted.
Truncate the UGCALL table. Check the disk space once truncate operation has been completed.
Re-import the data exported in step (2) into the UGCALL table and verify that the import is successful.
Check the disk space usage once more to see if remaining space is sufficient.
Yes, deleting row-at-a-time by a cursor will cause the same problem.
As noted, only a TRUNCATE TABLE will delete all rows without logging them individually. It uses less log space, but still some.

Microsoft Sql Server Managment studio backup size goes negative

The problem is that I need to explain the different sizes of backups that are being made of a database in a plant. Sometimes the difference between the sizes is in negative, even though that there is no data being deleted from the system.
Datum Backupfile-file Size KB Diff
6/1/10 backup201006010100.bak 3355914
7/1/10 backup201007010100.bak 4333367 977453
7/2/10 backup201007020100.bak 4355963 22596
7/3/10 backup201007030100.bak 4380896 24933
7/4/10 backup201007040100.bak 4380404 -492
8/1/10 backup201008010100.bak 4507775 1151861
8/2/10 backup201008020100.bak 4507777 2
8/3/10 backup201008030100.bak 4532492 24715
8/4/10 backup201008040100.bak 4584028 51536
On 7/3/10 and 8/1/10 there was no production. On other days the production is mostly consistent hence the database is expected to have a pretty much linear increase in size, but how is it that the size goes to negative.
In the maintenance plan the the tasks are: Backup Database Task (Type: Full Append Existing) -> Shrink Database (Leave 10% free space)
The last step of the backup process is to append data from the log that reflects any changes made to the database during the backup process, this could account for the difference you are seeing.
SQL Server have 2 step process of storing your data. First, your data goes into log file, and it not only data that you inserted, but also the whole list of operations SQL performed on your data. So, if something wrong happens, SQL can 'replay' your transactions.
At some point CHECKPOINT happens, ans data gets written into data file. Log files have a tendency to grow and shrink.
During BACKUP, SQL will write data and log files EXACTLY as they look at the point of BACKUP. That's why you can see that difference in size.

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